you're seeing a lot of law enforcement, the national guard. we've heard the navy is assisting the investigation. the back bay, if you've been to boston, is usually a very popular area, a very busy area, especially after the marathon. these bars are going crazy usually after the marathon with people celebrating. right now everything is shut down. everyone around here is looking for answers. they're coming up to reporters, going up to police officers, trying to figure out why anybody would do this. of course, there are so few answers as of now. again, the white house and homeland security chairman are saying it appeared to be terrorism. it happened around the four hour mark of the race, around the finish line. that's when most of the racers usually finish. it looks like it was intended to cause the most damage. right afterwards there was certainly a scene of chaos. the first explosion it seemed people didn't know quite what happened. maybe it could have been an accident. 15 seconds later when the second explosion went off, people knew something